Action Points

Be aware that RA patients with fibromyalgia were more likely to have worsening of functional status over time than those without.

Fibromyalgia is associated with worsening function in rheumatoid arthritis (RA) patients, and psychosocial distress does not fully explain the relationship, results of a new study suggest.

The analysis, published in Arthritis Care & Research, showed that a greater number of fibromyalgia symptoms predicts a decline in functional status in RA, which led the authors to conclude that fibromyalgia is a "spectrum disorder" with a continuous range of severity, rather than a "dichotomous entity."

Assessing fibromyalgia in RA patients may identify those who are more likely to experience clinically important declines in functional status, said Yvonne C. Lee, MD, of Brigham and Women's Hospital in Boston, and colleagues.

The researchers noted that fibromyalgia is a debilitating syndrome characterized by widespread, non-articular pain. The condition is more common in RA patients, with a prevalence of about 20%, compared with 2.5% in the general population.

The analysis included a subgroup of 209 RA patients from the Brigham and Women's Hospital Rheumatoid Arthritis Sequential Study (BRASS), all of whom completed questionnaires every 6 months and underwent yearly physical examinations that included lab tests.

The investigators assessed the symptoms and status using the Poly-symptomatic Distress (PSD) scale. Fibromyalgia was defined as a score of 13 or higher on the PSD scale.

RA disease activity was measured by the Disease Activity Score in 28 joints using C-reactive protein (DAS28-CRP). The researchers also assessed psychological distress using the Hospital Anxiety and Depression Scale (HADS), which ranges from 0 to 42, with higher scores indicating more distress.

The primary outcome for the study was a change in MDHAQ score at 2 years.

Of the 209 subjects, 53 were excluded due to missing data or loss to follow-up. Of the 156 remaining subjects, 85.9% were female and 93.6% were Caucasian. The mean age of the participants was 58.5, and mean RA disease duration was 15.4 years.

About 16.7% of the RA patients had fibromyalgia. Compared with those without fibromyalgia, this group had significantly higher baseline MDHAQ, HADS, and DAS28-CRP scores; pain intensity; and corticosteroid use.

An examination of the trend in HADS over the study period found that only the RA patients without fibromyalgia had statistically significant increases in scores, and in both groups, the increase in HADS score was small and unlikely to be clinically meaningful. "This suggests that the worsening of functional status in the RA-with-myalgia group cannot be fully explained by worsening psychosocial distress," the researchers said.

Baseline corticosteroid use was higher among patients with fibromyalgia than in those without. This likely indicates higher pain levels in those with fibromyalgia, which was reflected by the large difference in baseline pain intensity between the two groups: "It is not clear whether this difference in pain reflects differences in inflammation," Lee et al wrote. "This area is in need of further investigation."

Assessing fibromyalgia using the PSD scale may identify RA patients who are most likely to experience worsening function. "These individuals may benefit from treatment programs, such as physical and occupational therapy, targeted towards maintaining and/or improving physical function."

A limitation of the study, the authors said, is that fibromyalgia was defined according to the 2011 modified American College of Rheumatology (ACR) preliminary diagnostic criteria, which have not been formally endorsed by the ACR. Also, the prevalence of fibromyalgia and distribution of PSD scale scores in study participants, who had a mean disease duration of more than 15 years, likely differs from those in patients with early RA.

Asked for his opinion of the study, Roland Staud, MD, of the University of Florida, pointed to the small number of patients: "It's very difficult to draw conclusions from a small sample like this."

He also wondered how it could be beneficial to give RA patients suffering from pain, depression, and anxiety a label of fibromyalgia: "It's like lopping off the worst patients with rheumatoid arthritis and giving them a label of fibromyalgia, instead of just saying that these are patients with RA who are more affected by the illness than other individuals," Staud said.

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